1. Field of the Invention
This invention relates generally to the field of low current switching and specifically to reed relay shielding.
2. Description of the Related Art
Switching applications commonly use reed relays for connecting or disconnecting selected circuits. Typically, a set of three reed-type switching elements is surrounded by and operated by a single operating coil. For example, the switching elements may be normally open so that a pair of leads associated with each element is electrically disconnected. When the coil is energized, the three elements close, thereby connecting the leads.
Reed relays are used in low current switching assemblies adapted to connect selected circuits in an equipment testing environment. Circuits of a device under test are connected to a switching matrix that includes a plurality of relay assemblies. Test equipment is also connected to the matrix such that selected circuits of the device under test are connectable to selected test equipment inputs by operation of the relays. Three circuits, two signal circuits and one ground, neutral, or shield circuit, are switched simultaneously by a single relay assembly.
In such a testing environment, a high degree of accuracy and consistency is desirable in the signals conducted through the relays to achieve accurate test results. Because the currents tend to be very low (on the order of 1.times.10.sup.-12 A), the signals are susceptible to interference and leakage. Insulation and shielding can reduce interference and leakage. For example, copper foil is connected to one of the switching element leads and wrapped around the elements. The foil is connected to the center, that is, "guard" lead in a three element assembly. Such an arrangement has reduced leakage, however, further improvements are desirable.